A conventional transformer comprises inductors consisting of electric wire wound onto a core forming a magnetic circuit. These heavy and bulky elements are particularly troublesome when it is desired to use them in miniaturized electronic circuits. Attempts have therefore been made to replace such elements by electronic circuits capable of performing the same functions. A voltage v.sub.1 with a frequency F = (.omega.2.pi.) applied to the primary of a transformer generates therein a current i.sub.1 which causes a current i.sub.2 with a voltage v.sub.2 to appear in the secondary. The convention relationships between these currents and voltages are written as: ##EQU1## WHERE L.sub.1, L.sub.2 are the values of the primary inductance and of the secondary inductance, respectively, and M is the mutual induction coefficient of the transformer.
Quadrupoles that satisfy expressions (1) and, therefore, provide a transformer function equivalent to that of a transformer have been developed in the past.
However, the prior art circuits are generally costly because they require an excessive number of operational amplifiers.